1. Field of the Invention
This invention relates to an electronic apparatus, e.g. a portable computer, including an antenna for radio communication.
2. Description of the Related Art
In recent years, for electronic apparatuses such as a personal computer, apparatuses including radio communication devices such as a wireless LAN and Bluetooth (R) have become popular. In this type of radio communication system, radio waves, for example, of a 2.5 GHz or 5 GHz band are used. Moreover, as antennas for radio communication, various antennas such as a dipole antenna, helical antenna, slot antenna, and inverted F-shaped antenna are used for each type of
Additionally, a resonance frequency of the antenna is determined by shape, size, and peripheral environment of the antenna. Usually, a certain resonance frequency band is allocated to one antenna. Therefore, when a plurality of radio modules having different frequency bands from one another are used, a plurality of antennas have to be installed for these respective radio modules, and a problem of installation space occurs.
In relation to a solution of this problem, Japanese Patent Application Publication (KOKAI) No. 2002-190708 discloses a dual band antenna in which two resonance frequencies are imparted to one antenna, and a triple band antenna in which three resonance frequencies are imparted.
However, there is a limitation in the resonance frequency which may structurally be covered by one antenna, and with a predetermined number of (e.g., three or more) frequencies, the antenna size becomes very large, and the antenna shape also becomes complicated. Furthermore, when a plurality of resonance frequencies are assigned to one antenna, a usable frequency band is narrowed.